This application relates generally to antennas. More specifically, this application relates to reflectarray antenna systems.
The use of antennas in space, such as on satellites or spacecraft, presents challenges beyond those encountered in the terrestrial use of antennas. In particular, the need to locate antennas in space makes the processes for both the manufacture and use of such antennas much more sensitive to cost, mass, efficiency, stowability, deployment, and other considerations than is true for their terrestrial counterparts. In many respects, these heightened concerns have limited the way in which technology that is very suitable for terrestrial applications may be extended to space applications.
One specific application in which this is evident is in the use of electronically steered antennas, in which an electromagnetic beam is steered by using electronic phase shifters on a physically flat reflector, rather than by using physically shaped reflectors. One advantage to the use of such antennas is that the steering characteristics may conveniently be adjusted electronically rather than requiring physical adjustments. This could have significant advantages in space applications where reduction in vibrations that otherwise result from physical adjustments could be avoided. This is especially true, for example, given the large scan-angle (>±60°) applications used in some satellite applications. While such electronically steered antennas have found significant terrestrial applications, their use in space applications has been hampered by efficiency and other considerations. In particular, electronic phase-shifter components often have insertion losses that may be acceptable for terrestrial applications, but which are too large for space applications. The large insertion losses associated with the phase shifters result in increased output power required of the transmitter, thereby generally increasing cost, power-supply requirements, and thermal management resulting from the increased need for power dissipation. In addition, such electronic phase-shifter components also require radio-frequency (“rf”) electrical connections, which add complexity to the design and decrease reliability.
There is, accordingly, a general need in the art for improved antenna and antenna-component designs that mitigate such factors so that they may be more readily used in space applications.